Sodium-22 is well suited as a radioactive tracer due to its relatively long half life (about 2.6 years) and its strong gamma ray emission (about 1275 KeV) with 99.9 percent abundance. Its uses as a radioactive tracer are principally in biological and geological fields, e.g., as a radioactive tracer for logging data in subterranean formations such as oil wells. Additionally, sodium-22 can be used in intense slow positron beams.
Proton irradiation of targets for radioisotope production is a common process. Often, in the proton irradiation of, e.g., molybdenum or rubidium bromide, the target material is encapsulated in aluminum or an aluminum alloy. The irradiation of the aluminum in such encapsulation material results in the production of sodium-22. However, no convenient separation process has previously been known, especially a separation process from aluminum alloys.
U.S. Pat. No. 4,894,208 describes a distillation process of separating sodium-22 from aluminum, a process which is vastly different from the presently described process. Additionally, it is described that the distillation process requires the use of a graphite cup as molten aluminum forms alloys with metal, e.g., Monel alloy, cups from which sodium does not distill.
It is an object of the present invention to provide a process of separating sodium-22 from an irradiated aluminum target and especially from an irradiated aluminum alloy target.